The present invention relates to a motor-driven compressor.
Japanese Laid-Open Patent Publication No. 2010-59809 discloses a motor-driven compressor that includes a compressing portion for compressing and discharging refrigerant, an electric motor for driving the compressing portion, and an inverter (drive circuit) for actuating the electric motor. The motor-driven compressor disclosed in Japanese Laid-Open Patent Publication No. 2010-59809 includes a motor housing member and a front housing member, which is secured to the front side of the motor housing member. The electric motor and the compression portion are accommodated in the area between the motor housing member and the front housing member. An inverter housing member is secured to a bottom (partition), which is at the rear of the motor housing member. An inverter accommodating chamber is defined between the bottom of the motor housing member and the inverter housing member. The inverter accommodating chamber accommodates the inverter, which is fixed to the bottom of the motor housing member. A part of an upper portion of the motor housing member forms a passage forming portion, which protrudes radially outward. The inner circumferential surface of the passage forming portion and the outer circumferential surface of the stator (stator core) of the electric motor define a wiring passage (passing area) inside the passage forming portion.
A cluster block, which is made of plastic, is arranged in the wiring passage. The cluster block is fixed to the outer circumferential surface of the stator via a joint member. A conductive member, which is electrically connected to the inverter, is fixed to the bottom of the motor housing member. The conductive member extends toward the wiring passage. Lead wires are drawn from the electric motor toward the wiring passage. The conductive member and the lead wires are electrically connected to each other via connection terminals in the cluster block. When assembling the motor-driven compressor, the cluster block is fitted into the motor housing member while being fixed to the outer circumferential surface of the stator, and is arranged in the wiring passage.
The motor housing member has a suction port that opens to the wiring passage. In the motor housing member, the suction port is located at a position closer to the bottom than the position at which the cluster block is located. The front housing member has a discharge port. When refrigerant is drawn into the motor housing through the suction port, the refrigerant cools the bottom. The cooling of the bottom by the refrigerant in turn cools the inverter fixed to the bottom.
A clearance is formed between the cluster block and the motor housing member of the motor-driven compressor disclosed in Japanese Laid-Open Patent Publication No. 2010-59809, so that the cluster block and the motor housing member do not interfere with each other during assembly of the motor-driven compressor. Further, the stator is fitted inside the motor housing member by shrink fitting. In the shrink fitting, the motor housing member is first heated for expansion. Then, the stator is inserted into the motor housing member.
Subsequently, as the temperature of the motor housing member drops to ordinary temperature, the motor housing member shrinks and is pressed against the outer circumferential surface of the stator. That is, since the temperature of the motor housing member is raised when it is heated and expanded, the cluster block may be melted when contacting the heated motor housing. The clearance is provided between the cluster block and the motor housing member to prevent such melting of the cluster block.
Such a clearance between the cluster block and the motor housing member allows refrigerant that has been drawn into the motor housing member via the suction port to flow to the front housing member (discharge port) through the clearance. This reduces the amount of refrigerant flowing toward the bottom of the motor housing member, which hinders efficient cooling of the bottom by the refrigerant. As a result, the cooling performance for the inverter deteriorates.
Such a problem is substantially common to any type of motor-driven compressors having a passing area that receives a part of an electrical connection portion for electrically connecting a conductive member with an electric motor.
Further, in a motor-driven compressor in which an inverter, a compressing portion, and an electric motor are arranged in that order along the axial direction of the rotary shaft of the electric motor, a passing area is defined by the inner surface of the housing and the outer circumferential surface of the compressing portion, and a part of an electrical connection portion is passed through the passing area. In this case, some high-temperature and high-pressure refrigerant, which is generated through compression in the compressing portion, flows toward the partition through the passing area to undesirably warm the partition. As a result, the cooling performance for the inverter deteriorates.